Bedrock Geology #Wiarton repost

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During a delegation at a June 3 South Bruce Peninsula council meeting, interest was sparked over the Peninsula’s expansive network of Karst systems that contribute to groundwater and surface water features, as well as river systems and lakes.

Karst features are unique landforms that are developed by the flow of groundwater penetrating the sub-surface of the Bruce Peninsula’s dominant limestone and dolostone geology. Most of the Bruce is covered by Karst landforms, and are sometimes passed unnoticed because of their unassuming appearance.

James Hamilton, from Wilfred Laurier University’s Environmental Studies department in Waterloo, made a presentation to council specifically noting the unique Karst systems around Hepworth, advocating for their identification and protection, as Karst system aquifers are highly vulnerable to contamination, and represent “some of the best water quality displayed in the province.”

“The most important aspect is the hydrology,” said Hamilton. “Karst features are a window into bedrock aquifers. Water moves into a Karst landform, like a small sinkhole, and that aquifer has the capacity to store and transmit very high quantities of high quality water.”

Hamilton has been investigating the Karst systems near Hepworth’s Spring Creek, and Skinner’s Marsh – a system that originates near Mountain Lake in the Georgian Bluffs – with the assistance of the Hepworth Anglers Club for the last few years.

“We can extract that water through groundwater wells, the water also makes it way back to the surface through a network of springs that typically feed very high quality streams – so you get these cold water streams with lots of base flow, and they become the streams that support strong sports fisheries.”

Hamilton told a captivated council that some sinkholes can take on 500-600 liters of water per second, and that a sinkhole draining from Skinner’s Marsh could in fact be the largest disappearing stream in southern Ontario, supplying 40-50% of the water that contributes to the Sauble river. The ecosystems that flourish because of the high quality of oxygen rich water support a teeming sport-fishery, with Coho salmon, Brook and Rainbow trout using the rivers and streams to spawn.

Hamilton also noted that land use is becoming an issue that threatens Karst systems. In Hamilton, some Karst aquifers have already been paved over. In Hepworth, two developments could interfere or contaminate the local aquifers, meaning that ultimately, drinking water supplies, the Sauble river and Lake Huron could be affected. He added that Bruce county planning has asked the MNR about possible data collection to appropriately manage developments and Karst systems that may come into contact. However, the MNR doesn’t have that data as of yet.

“We only have very general data on the distribution of Karst, if we really wanted to do better planning, we would have more detailed information available. The problem with that is, it’s very labour intensive to gather that data. Typically, it’s done on a case by case basis.”

Counc. Jim Turner, noted that “both projects planned for the Hepworth area required Karst studies.”

Hamilton stated “In any kind of development that has the potential to impact surface water and ground water, you have to make sure you have the appropriate measures in place to limit that potential impact. You don’t want large quantities of contaminated storm water moving into the sub-surface. If that becomes part of the recharge of the aquifer, then the aquifer will be diminished.”

South Bruce Peninsula Mayor, John Close, said that the province would need to be convinced more when this discussion brings up aggregate. “Aggregate is a high provincial priority,” he said. “These are geological land formations that are throughout our municipality, and its very important to be informed. As development takes place, we don’t want to lose these land features, because they’re obviously feeding our streams and feeding our drinking water.

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